Outlook for the remainder of hurricane season

Atlantic tropical cyclone activity finishes its peak phase in mid-October, and takes a major downturn after about October 20 (Figure 1). Since the current active hurricane period began in 1995, the last half of October through the end of hurricane season has given birth to an average of 1.7 named storms, 0.8 hurricanes, and 0.3 intense hurricanes. These numbers are nearly double the long-term climatological averages for the past 100 years. So far this year, only one tropical storm has hit the U.S.--Tropical Storm Claudette. If no more tropical storms make landfall in the U.S., it will be the first year since 1993 to see only one tropical storm hitting the U.S.

Figure 1. Atlantic hurricane season activity over the past 100 years.

Late October and November storms tend to form from tropical waves that come off the coast of Africa, or from the remains of old fronts that push off the coast of the U.S. As we can see from the track plot of all last half of October storms (Figure 2), there is a lot of activity during the period, but relatively few storms form out near the African coast. The water temperatures off the coast of Africa are starting to cool and be marginal for hurricane formation, and the African Monsoon is waning, leading to fewer African waves coming off the coast. Wind shear is also starting to increase, as part of its normal fall cycle.

Climatology of late-season major hurricanesLet's examine the possibilities of getting a late-season major hurricane, since those are the storms we care most about. Since 1960, there have been twelve hurricanes that have existed as major Category 3 or higher storms after October 15. Eight of these have occurred since 1995: Omar of 2008 (Cat 4, Lesser Antilles), Paloma of 2008 (Cat 4, Cayman Islands and Cuba), Wilma of 2005 (Cat 4, Mexico; Cat 3, SW Florida), Beta of 2005 (Cat 3, Nicaragua), Michelle of 2001 (Cat 4, Cuba), Lenny of 1999 (Cat 4, northern Lesser Antilles), Mitch of 1998 (Cat 5, Honduras), and Lili of 1996 (Bahamas, Category 3). The other four were Joan of 1988 (Cat 4, Nicaragua), Kate of 1985 (Cat 3, Gulf of Mexico), Ella of 1962 (Cat 3, west of Bermuda), and Hattie of 1961 (Cat 4, Belize). Wilma of 2005 was the only major hurricane since 1960 to hit the U.S. after October 15. The highest risk region for late season major hurricanes is the Western Caribbean, along the coasts of Nicaragua, Honduras, Belize, Mexico, and Cuba. So, we can say with high confidence that most of the U.S. coast can relax. Only the west coast of Florida, Florida Keys, and South Florida need to still be concerned about the possibility of a major hurricane. The Lesser Antilles Islands, Puerto Rico, and Hispaniola are also at low risk for a major hurricane the remainder of the season.

Figure 2. Tracks of all tropical storms and hurricanes since 1851 that formed October 16-31.

Sea Surface TemperaturesSea Surface Temperatures (SSTs) are 0.5 - 1.5°C above average over the Western Caribbean and Gulf of Mexico (Figure 3), the primary formation areas for late October storms. So, there is still plenty of fuel for a major hurricane to form. Note also the tongue of warmer than average SSTs extending out into the Pacific Ocean from the coast of South America, the signature of weak El Niño conditions.

The jet stream in mid-October is more active and extends further south, which brings higher levels of wind shear to the Atlantic. The more active jet stream also acts to recurve storms more quickly. Any system penetrating north of about 20 degrees north latitude we can expect to recurve quickly to the north and northeast this late in the season. The most recent 16-day forecast from the GFS model predicts a period of high wind shear over the tropical Atlantic over the next ten days (Figure 4). Beginning on October 25, wind shear is expected to fall again over the Western Caribbean, and we need to be alert for tropical storm formation then. Indeed, the latest run of the GFS model is predicting a large area of surface low pressure will form in the Western Caribbean during the last week of October, an indication that hurricane season may not be over yet.

El NiñoEl Niño conditions, which typically bring higher wind shear to the Atlantic and interfere with hurricane formation, continue to be present in the tropical Eastern Pacific. It is probably the case that some of this year's inactivity can be attributed to El Niño. However, as I discussed in a post earlier this year, El Niño events that warm the central Pacific more than the eastern Pacific (called "modiki" El Niño events), tend to bring less wind shear to the Atlantic. In recent weeks, El Niño conditions in the Eastern Pacific have trended more towards a "modiki" type event, with a large amount of warming in the Central Pacific. This shift in the El Niño may bring lower wind shear to the Atlantic over the final month of hurricane season.

Figure 4. Wind shear forecast for October 23, 2009, as produced by the 00 UTC run on October 14, 2009 made by the GFS model. Wind shear below about 8 m/s (roughly 15 knots, red colors) is typically needed to allow tropical storm formation. There aren't too many red-colored areas over the prime breeding grounds for tropical storms in the Atlantic over the next ten days in this forecast.

SummaryGiven how quiet the tropics are at present, and the forecast of a high wind shear regime lasting until October 25, I doubt any tropical storms will form over the next ten days. If we do get something, it would probably be in the middle Atlantic between Bermuda and the Azores, far from land. However, I am still wary of the possibility of a hurricane in the Caribbean the last week of October or in November this year. There is evidence that the Atlantic hurricane season is starting earlier and ending later in recent decades. Dr. Jim Kossin of the University of Wisconsin published a paper in 2008 titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high". We had two major hurricanes in the Caribbean after October 15 last year, and I give a 60% chance that we'll get a named storm in the Caribbean before hurricane season ends on November 30. Hurricane season is not over--it's just in hibernation.

Happy Valley to become Yucky ValleyWinter is fast approaching, and the season's first major snowstorm for the U.S. East Coast is coming this weekend, according to the wunderblog of Wunderground's Dr. Rob Carver. Conditions will be particularly nasty on Saturday in Happy Valley, where Penn State is situated. The surrounding hills may get 4 - 12 inches of snow, and rain mixed with snow with 36°F temperatures are expected for Saturday's Penn State - Minnesota game. Ugh, winter! I'll have a forecast for the coming winter in a post sometime in the next week.

The Senate has not yet voted on the proposal to cut NOAA funding. I will post a report when the vote occurs.

Based on Dr. Master's forecast the formation of a major hurricane around the last week of Oct is better than 50% in the Caribbean. Can anyone guess that far out what the likeliehood of a CONUS landfall would be? I imagine that is a stretch to call but just curious what the shear and steering currents will be like at that time...

JAKARTA, Indonesia -- A strong earthquake rattled the Indonesian island of Java on Friday, sending panicked people into the streets of the capital city, Jakarta.

The U.S. Geological Survey put the quake's magnitude at 6.1 -- lowering it from an earlier magnitude of 6.5.

The epicenter was located in the Sunda Strait -- the narrow body of water between Java and Sumatra islands, about 115 miles (185 km) southwest of Jakarta, according to the USGS.

It struck shortly before 5 p.m. local time (6 a.m. ET).

The quake prompted a mass evacuation in downtown Jakarta. There was no sign of any initial damage, CNN producer Andy Saputra said.

It is the latest in the series of quakes to have rattled Indonesia, including strong quakes on September 30 and October 1 near the island of Sumatra.

More than 1,000 people are believed to have died after the quake destroyed buildings in the city of Padang, the capital of West Sumatra.

Friday's quake did not last long, and was not nearly as powerful as the 7.0-magnitude quake that shook Jakarta on September 2, causing high-rise buildings to sway, according to Reuben Carder, a reporter with Dow Jones.

"I played with my toys and took a nap," Falcon told a group of reporters outside his home Thursday afternoon.

"He says he was hiding in the attic," said Falcon's father, meteorologist Richard Heene, clutching his son. "He says it's because I yelled at him. I'm sorry I yelled at him."

But in a later interview with CNN's "Larry King Live," Falcon said he heard his parents call for him from the garage. When asked by his father on-air why he didn't respond, the boy replied, "You guys said we did this for the show."

When Heene was pressed by Wolf Blitzer, who was filling in for King, to explain what his son meant, he became uncomfortable, finally saying he was "appalled" by the questions. He added that Falcon was likely referring to all the media coverage."""............

Quoting 954FtLCane:(boy in a ballon)...Honestly the more and more I see this story the more I think it was a publicity stunt... oh by the way the family also participated in wife swap.... call me a cynic but... hmnmmmmmm ... there's just something fishy.. I may be wrong but...hmmm

Quoting 954FtLCane:(boy in a ballon)...Honestly the more and more I see this story the more I think it was a publicity stunt... oh by the way the family also participated in wife swap.... call me a cynic but... hmnmmmmmm ... there's just something fishy.. I may be wrong but...hmmm

Just re-quoting myself from yesterday right after they found the boy.....

Cavin, that is a very nice biography. You sound like a nice young man with many goals of life ahead of you. I spent 14 years in the NWS as a Met Tech but never got my bachelor's degree. That was a huge mistake but life has it's reasons. I am glad you finished college and you should go forward...

By the way, I hve been to St. Kitts many years ago on a Windjammer Cruise. I actually was on the Fantome, a sailing ship that went down in Hurricane Mitch off Nicaragua.

Quoting AwakeInMaryland:Quiet season, quiet in the blog. Hurricane Bill had me worried; I was afraid our east coast beaches would be decimated. The "invisible shield" saved us this year.Now it's just this nasty yucky gloomy cold.On the topic of the north pole ice melting -- I heard that similar conditions existed in the 1700s, that explorers could get through. So that gives me some small hope that it's cyclical, that we haven't destroyed the planet (yet). I don't know enough to get into an intelligent climate change discussion. I just hope science and good will can make things better.

Wikipedia has articles on the Northwest and Northeast passages, for someone who likes history more than I. It wasn't open w/o icebreakers till 3 years ago was it? All I know is they first got through both in the 1800s. Maybe they did it by embeding the ship into the moving ice, like the Fram? Unless they had icebreakers in the 1800s?

That is something we could look at in the case of a TC expected to be undergoing intensification. There have been some studies showing that an uptick in TC lightning leads to intensification in most cases (sometimes with a lead time of 24 hours).

That is if we don't forget what a TC in the Atlantic looks like.

A pretty good amount of lightning around Rick, but I don't know how what we are seeing compares to that for a precursor to intensification...tho it is in the forecast.

/>meeting deadlines at work can be compared to giving birth. today was my big day and we all did it together. just sharing that cuz i'm basically worn out after weeks of effort...anyhow. Dr. Masters sounds like he still thinks something could stir up in the Caribbean. But sure doesn't look like it's gonna happen tonight. peace all. and prayers for the filipinos. oh yeah, and thank god they found little falcon. it doesn't matter how or where. he made it. and to me, that is a miracle to be celebrated. goodnight! and sweet dreams of beautiful places. :)